There is known a substrate processing apparatus of this type having ring-formed retainers for supporting substrates, one by one, on a holder (boat) for sustaining a plurality of substrates. For example, a structure is known that has retainers to be placed in contact with a substrate only the backside thereof in a region corresponding to a region extending from the edge to device fabrication area of a substrate (e.g. Patent Document 1).
Patent Document 1: Japanese Patent Unexamined Publication No. 2005-86132